Hydraulic steering on 31' sailboat

[TrentePieds]

This boat was designed so that under full sail, i.e. full main and #1 jib, on a beam reach in 12 or 15 knots of wind she would track straight. That was achieved by so placing the mast that she had the right "lead", i.e the right moment arm between the Centre of Effort of the sail plan and the Centre of Lateral Resistance of the underwater profile WITHOUT counting the deadwood-hung rudder when healed 12 or 15 degrees.

As the boat heeled, the weight of the rudder would, due to the rake of the hinge line, cause it to deflect to the leeward side, thereby introducing a hydrodynamic force that would tend to cancel out the boat's tendency to head up that resulted from the CE moving outboard to the leeward side.

Changes to the shape of the waterline plane also come into play but are too complicated to discuss here.

When so sailing, the rudder merely "trails behind" and is not counted in the calculation of the position of the CLR. When so sailing, if you now grasp the tiller and hold it steady midships, the rudder DOES get counted in the calculation of the CLR because the now cannot deflect. That has the effect that the CLR moves AFT, and the "lead" gets longer, with the result that the boat's tendency to "head up" is attenuated.

If holding the tiller steady midships does not cause the boat to "track", then the tiller must be hauled further to the windward side, i.e. "to weather", and we say the boat has "weather helm", Carrying significant weather helm increases resistance slowing the boat and should be avoided.*

Thus, the "hardness" of the helm, the force required to haul the tiller to weather to prevent the boat "rounding up" or "griping" and going out of control, is the single best indicator of whether you are carrying the right area of canvas for the given amount of wind. Any "improvement", such as hydraulic steering, is therefore detrimental to good seamanship and is in any case not required in a boat as small as 31 feet. Wheel steering becomes a necessity only in boats so big that a well grown man's strength cannot handle the tiller forces. IMO wheel steering in small boats is misbegotten ostentation :-)!

The sail plan should be so arranged that in any given strength of wind the boat will heel about 15º. That is a function of TOTAL sail area. It should also be so arranged that for any given total sail area, the RELATIVE areas afore and abaft the DESIGN CLR are such that the ACTUAL CLR, when sailing, coincides with the design CLR. You know that that is so when the boat tracks at 15º heel without excessive weather helm. This desirable quality is achieved by carefully calculating the individual positions of the reef points of all sails.

But let's see what Harmony has to say after his next sail :-)

TrentePieds

[Bowdrie]

In the waning days of the CCA we saw two things emerge that changed yacht design, both in the underwater profile of the hull, (CLR,) and the sailplans, (CE).
#1, The advent of Dacron sails.
#2, Big winches that could sheet-in big headsails.
In the days of large low aspect mainsails, (long booms,) and small jibs, the act of reefing the main could shift the CE over a fairly broad range.
When boats became "headsail driven", it forced the designers to locate the CLR further forward, otherwise the "lead" of the CE in respect to the CLR would get too far forward.
Removing a lot of keel structure, (deadwood,) on that boat without changes to the sailplan has undoubtedly "upset the apple cart" with respect to the relative positions of CLR vs CE.

[Harmony31_NHP]

Thank you all! This is great and I very much appreciate your input. I'll be sure to post my findings after I get a chance to take her out for some sailing.
Meanwhile I'm stuck on another idea, but I'll post that as a separate thread (using my old keel water tank as a coolant reservoir for the engine to enable year-round use in these freezing latitudes)...

[Harmony31_NHP]

It's been a while and I have only had the chance to sail in very light winds but now that the boat is up I think I can relate my previous feeling of heavy steering more towards an overall feeling of sluggish behaviour. The steering actually feels fine and the boat reacts with weather helm. To me the rudder looks like it has been designed and installed by someone who knows what they are doing (images attached). As the boat made its' way out of the water I could see that the whole hull was covered by barnacles (image attached) and hopefully a good cleaning and reworked anti-fouling coating will improve the behaviour a lot. Aside from that I think I need to rework the trailing edge of the keel (where the old rudder trailed before removal) and I am curious about hearing your thoughts about how much you think an improved edge profile can affect performance (image of current edge attached).

[TrentePieds]

Oh, yes, oh, yes, oh yes, Harmony! Get the crud off her, and she'll feel like a whole new boat :-)!!!

Until you've brought a boat that's been in the water for a year or two some miles to a hoist and then taken her away again after having her bottom wiped and nicely painted, you can have no comprehension of how important it is to keep 'er clean :-)!

If you can get her in and out the same day, your body will retain the memory of her behaviour while coming so you can compare it with her behaviour going.

'Nother lesson to learn from your experience is that it's easy to misconstrue the symptoms when something seems to be amiss. But we are here to help you with that — for now. For as you gain experience, you won't be needing our help with that :-)

As for the trailing edge of the keel, that's perfectly normal, and since the boat is not an out-and-out racing machine, there is no need to do anything about it. On the other hand, there would be no harm in fitting a fairing strip. I doubt, however, that you'd be able to perceive even the least improvement in performance.

While she's out, make sure you get zinc on the prop shaft! I don't see one.

TP

[barnakiel]

It is pretty clear, I think, that removing the original rudder and adding a different one, well aft, would cause lee helm in this boat.



Hydraulics will not change that.


Now you can :


- add a stub (fixed) area - where the rudder used to be,
- go fractional (small jib, no genoa sails),
- move the mast aft ...


etc.


Or simply move back to the original design, unless it is known to be seriously flawed (was it?).


A 30 footer that asks for anything else that two fingers on the tiller ??? Well ...


It is very highly probable that your boat is off balance, and hydraulics WILL NOT fix the problem. Moving the rudder, or the mast, could.


b.

[donradcliffe]

Hydraulic steering systems are designed to leak, and would be a last resort for a boat of that size.

You will need to sail it again wit ha clean bottom to see if it needs a steering change.

The drag caused by the keel is proportional to the width of the unfaired portion. That boat looks like you might as well be dragging a vertical 2x4 timber of the appropriate length.